The present invention relates to a process for restoring magnetic recording tape damaged by xe2x80x9cSticky Shedxe2x80x9d syndrome.
Tape recording technology had its first beginnings in the late 1930s and early 1940s, and has continued to this day with a stream of changes and improvements to magnetic tapes and also to tape machines. Various standards for both tape and machines have also developed over time. The appeal of tape-recording is that one is able to form an analogous magnetic memory bank of magnetic patterns and impulses that can capture all kinds of acoustic events when the tape is recorded and played back at another time. Thus, tape and tape-recording are invaluable for capturing all kinds of sounds from sound effects, speech, as well as acoustic or electronic music. Recordings contain a vast personal, cultural, artistic, and historical value as well as a substantial monetary value when these recordings are copied, sold and played.
Tape-recordings were a new and better technology that replaced the older cylinder methods, the older direct recording to acetate or wax discs, and wire tape recorders. Today, the tape-recording industry is large and active, but it is facing competition from the newer digital and computer technologies, which at least supplement tape-recording, and which may replace tapes, particularly so if the tape problem of xe2x80x9cSticky Shedxe2x80x9d is not solved and if tape-recordings are damaged or lost due to improper handling or destructive restoration efforts by those who do not understand the problems inherent in restoration, or who do not use a restoration process that best preserves tape and program integrity.
The earliest tapes used paper as a base for the tape. This did not work very well and the paper base was soon replaced by an Acetate Base. The Acetate Base is somewhat fragile and can be easily broken. Also, Acetate tapes need proper storage conditions of temperature and humidity to remain in good playing condition. In the early 1960s, a new Mylar Base material was invented that replaced Acetate. The Mylar Base tapes are much stronger than Acetate, and do not easily break, and also do not require rigid temperature and humidity control conditions to remain in good condition.
The other main element of a tape is the Oxide material and the binder chemicals that hold the Oxide to the Base. These Oxides and binders have undergone constant improvement over time. The Oxides range from Ferric Oxide to Chromium Dioxide to many variations thereof. The aim has been to get better and more powerful magnetic performance, a longer wear life, smoother surfaces, better frequency response, less noise, etc. The Binder is a chemical brew mixed with the Oxides, which is then processed to evaporate the solvents, leaving the Oxide coating on the Base, which is then rolled and smoothed out. The large tape rolls are then slit to various widths, and then put on reels for use on tape machines.
The third element in tape manufacture is the Backcoating. Backcoating was developed by Ampex. (now Quantegy) and other tape makers in the late 1960s, and added to tapes to improve the mechanical handling qualities of tapes by providing for a smoother tape wind and for reducing static build-up due to friction in the tape path of tape machines. Prior to the introduction of Backcoating in the late 1960s, tapes did not have Backcoating. Although Backcoating helps with these mechanical problems of machines of the day, the fact is there is a price to pay for using Backcoating which is that, over time, it causes the chemical breakdown of the tape and leads to the tape problem of xe2x80x9cSticky Shedxe2x80x9d which is damaging and is currently destroying many tapes which have Backcoating. The tape makers touted Backcoating as an improved product and thus customers demanded tapes that had Backcoating. Sales of Backcoated tapes increased, while the sales of non-Backcoated tapes decreased. Today, it is very difficult to even find non-Backcoated tape for purchase. Rarely, if ever, did any tape that did not have Backcoating exhibit the xe2x80x9cSticky Shedxe2x80x9d problem. Nearly every tape that has Backcoating has xe2x80x9cSticky Shedxe2x80x9d problems to a varying degree. Thus, Applicant has concluded that the Backcoating is the bad actor in this situation. While Backcoating may have helped with some mechanical issues in the 1960s, it left behind a chemical time bomb which is destroying tapes today and will do more destruction in the future until and unless a process is used to solve the xe2x80x9cSticky Shedxe2x80x9d problem. Backcoating is no longer needed as the problems it addressed either no longer exist or can be dealt with in other ways. Tapes need to have a long, safe, archival life, free of the xe2x80x9cSticky Shedxe2x80x9d problem, and the best way to do that is to end the manufacture of tapes with Backcoating. However, it is often necessary and/or desirable to play old Backcoated tapes and the xe2x80x9cSticky Shedxe2x80x9d problem makes the playing of old tapes difficult and endangers their future use.
A number of years after Backcoating was first applied to tapes, a new problem, which came to be known as the xe2x80x9cSticky Shedxe2x80x9d problem, arose. Tapes now became sticky, which meant they would not play properly and smoothly on a tape machine. Instead of normal playback, the tapes now would stick to various mechanical parts in the tape path of a tape machine. This sticking would not only cause noise, but as the problem got worse, tapes either would not play at all, or even worse, would shed debris on the playback head which greatly impaired getting the proper or full magnetic and sound signal off the tape. In the worst case situations, the sticking Backcoating would rip the Oxide off the base of the tape, thus completely destroying all the magnetic data on the tape. Also, the sticking would cause the tape speed to vary, causing xe2x80x9cflutterxe2x80x9d of the program during playback.
Tape companies, users, and owners of tapes went into a state of dread and panic about losing these tapes, which concerns continue to the present day. There are millions of tapes with the xe2x80x9cSticky Shedxe2x80x9d problem which has caused owners and users of tapes to face the grim prospect of losing, entirely, the valuable magnetic information on the tapes, or in getting inferior playback sound from these tapes. The xe2x80x9cSticky Shedxe2x80x9d problem has thus compelled the industry to commence an extensive and expensive effort to transfer the content of the xe2x80x9cSticky Shedxe2x80x9d tapes onto either digital media or other analog tapes.
The problem of xe2x80x9cSticky Shedxe2x80x9d is well known in the tape-recording industry and numerous articles have been published discussing the problem and proposed solutions.
In an article published in the Washington Post in May, 1989, Agfa Corporation was reported to have introduced a five step labor intensive process described as xe2x80x9cAgfa-NXTxe2x80x9d that xe2x80x9cinvolves a variety of techniques ranging from cleaning to heat.xe2x80x9d In the December, 1994, edition of Pro Sound News, it was reported by Eddie Giletti that:
xe2x80x9cTapes with shedding problems can be cured, at least long enough to get a good transfer. Several manufacturers offer this service, or it can be done in-house. A low-temperature (140 degrees F.) baking process was found to reactivate the binder. The pack must be perfectly smooth or the tape surface will become uneven. Baking time varies with tape width, starting with one hour for quarter-inch tapes up to several hours for two-inch tapes. Flipping the tapes every half-hour ensures that the heat is distributed evenly. Tapes must cool before use.xe2x80x9d
In the Nov. 29, 1995 edition of Radio World, an article titled xe2x80x9cClean and Restore Old Analog Tapesxe2x80x9d states the following:
xe2x80x9cHydrogen peroxide is the only solution recommended by Neuman for cleaning the surface or backcoat of a tape. It does not damage any of the tape""s chemical components and is safe to the user. By all means, do not use alcohol or other solvents as they may permanently damage the tape.
Peroxide will effectively clean off the mold and its antiseptic properties will help inhibit future mold growth.xe2x80x9d
In a publication dated Feb. 17, 2002, and issued by the Magnetic Reference Laboratory, Inc., report is given to the following:
xe2x80x9cFor temporary shed reduction on existing tapes, try placing the tape in an oven at 120xc2x0 F. (50xc2x0 C.) for about a day, as recommended by Ampex.xe2x80x9d
In a paper presented at the 113th Convention of the Audio Engineering Society, Oct. 5-8, 2002, titled xe2x80x9cArchiving Audio,xe2x80x9d the xe2x80x9csticky shed syndromexe2x80x9d is described and xe2x80x9cbaking sticky-shed tapes is a common method used to rejuvenate tapes with binder breakdown.xe2x80x9d
In the July/August, 2003 edition of Audio Media, an article titled xe2x80x9cArchiving Issues, Part One: Recommendationsxe2x80x9d states that the xe2x80x9csticky shed syndromexe2x80x9d xe2x80x9ccan usually be fixed temporarily by baking the moisture out of the tape (a practice, by the way, which also usually loosens any splices on the tape).xe2x80x9d
Thus, in the tape manufacturing and recording industry, virtually every solution for the xe2x80x9cSticky Shedxe2x80x9d syndrome involves baking the tape with those recommending this procedure providing no assurance that the procedure can be practiced more than once and, in most cases, strongly recommending that the information on the tape be transferred to another medium after the baking has been completed.
The sole reference recommending a chemical solution recommends the use of hydrogen peroxide to remove mold from a tape and specifically counsels against using alcohol or any similar solvent for fear of damaging the tape.
Applicant is also aware of the following U.S. Patents:
U.S. Pat. No. 4,849,839 to Tsubota et al. (assigned to Sony Corporation) discloses mechanical cleaning of video tape to remove small debris which gets on the tape. There is no mention of the Backcoating nor any mention of chemical cleaning of the tape.
U.S. Pat. No. 5,080,825 to Bradshaw (assigned to IBM) discloses a water-based solvent for cleaning a tape drive. There is no discussion of cleaning of the Backcoating nor is the water-based solvent sufficiently strong enough to chemically remove the Backcoating as contemplated in the present invention. The solvent disclosed by Bradshaw is applied to the Oxide side of the tape as compared to the present invention in which a solvent is applied to the Backcoating side of the tape. In the present invention, the Oxide side is dry-cleaned.
U.S. Pat. No. 5,236,790 to Medeiros et al. (assigned to Ampex Systems Corporation) discloses a supposed solution to the xe2x80x9cSticky Shedxe2x80x9d syndrome which requires heating of a magnetic recording tape to a level of at least 50xc2x0 C. for a time period of at least 3 hours. The present invention differs from the teachings of Medeiros et al. as contemplating removing the Backcoating of a magnetic recording tape using a solvent at room temperature without any heating of the tape.
U.S. Pat. No. 5,311,371 to Clark discloses a magnetic tape data recovery method which includes the use of baking applied to data tapes. Again, the present invention contemplates removing the Backcoating of a magnetic recording tape without resort to any elevation of temperature.
U.S. Pat. No. 5,638,236 to Scott (assigned to Sony Corporation) discloses the use of cleaning patches on a tape located on the Oxide side of the tape to periodically clean clogged tape heads. The present invention differs from the teachings of Scott as contemplating using a solvent to remove the Backcoating from a magnetic recording tape, and no chemical on the Oxide side of the tape period.
U.S. Pat. No. 5,786,949 to Sakamoto (assigned to Sony Corporation) discloses a magnetic transfer apparatus including a tape cleaning arrangement. Sakamoto contemplates vacuum cleaning of tape debris on air tape guides during high speed video duplication. Sakamoto solely contemplates removal of loose debris during duplication and does not contemplate nor solve the xe2x80x9cSticky Shedxe2x80x9d syndrome. Sakamoto does not contemplate using a chemical solvent nor dry-cleaning of the Oxide side of the tape as is the case in the present invention.
The baking methods are full of guesswork with little explanation why baking the tapes does provide for some relief to the xe2x80x9cSticky Shedxe2x80x9d problem. Applicant has found that Backcoating breakdown is the cause of the xe2x80x9cSticky Shedxe2x80x9d problem. Others blame the Binder. If the Binder were breaking down, the magnetic particles in the Oxide coating would fall off the tape. When Applicant cleans a tape machine tape path from contamination, a black residue is found to have been removed that is part of the Backcoating, not the orange color residue of the Oxide coating on the cotton swab cleaners. If the Oxide binder was really breaking down and falling off the tape, all is lost, and heating the tape up is not going to rejuvenate a binder or restore a magnetic pattern which is recorded on the tape.
In fact, heating a tape has negative consequences simply on the basis of the fundamentals of physics and chemistry. When a tape is heated, the Mylar Base material of the tape is expanded, which may loosen the Oxide and binder combination that was coated on the base during manufacture. Chemically, heating something up accelerates the aging process and starts other chemical activity going which uses heat as a catalyst for other mechanical and chemical changes to take place. Heating the tape also directly contradicts the general archival standard to control temperature and humidity to low and stable levels. Even if heating the tapes gives some short term benefit, the xe2x80x9cSticky Shedxe2x80x9d problem is not eliminated, but, in time, returns with even more severity and damaging results until such time as the tape is destroyed entirely.
The Backcoating is made of a complex organic chemical with a strong Carbon component. Organic chemicals are inherently unstable. Also, organic, Carbon chemicals are hydrophilic in that they attract water vapor and moisture. The result is the start of fungus growth, and the likely formation of carbonic acid or other chemicals which in turn attack the Mylar Base of the tape, the Oxide itself, and the Oxide Binder on the other side of the Mylar Base of the tape. Because tape is wound on reels, one layer of the tape""s Backcoating comes into direct physical contact with the Oxide and the Oxide Binder of the next wound layer of tape on the reel. The Backcoating has its own chemical changes going on internally, and it comes into direct contact with the non-organic Oxide that contains the invaluable magnetic particles which make tape perform its recording and playback functions. When different chemical elements such as Carbon, Water, and non-organic elements such as Iron Oxide come into contact, the result is a chemical reaction in which the Backcoating turns into a gooey consistency and glue, with a further chemical attack on the Oxide and the Binder which holds the Oxide to the Base. The baking of the tapes does nothing to remove these chemical ingredients from interacting with each other endlessly until tape destruction is complete.
The reason the baking method does provide some temporary improvement is twofold. First, the higher temperature drives off the moisture by evaporation, but it does so only for a short period of time until the Backcoating will again, in time, attract moisture back to the tape. Second, the Backcoating behaves in a manner similar to wax, in that, at room temperature, the wax is a sticky substance. When heated, wax, and similarly the Backcoating, will change from its sticky state to a liquid state, thus releasing its grip on the mechanical parts it contacts for a time. But this is no real final cure for the problemxe2x80x94it is a band aid. Removal of the Backcoating from the tape removes the chemical agents which are waging a chemical war against the Base and the Oxide. Ending the chemical war is what saves the tape from destruction, makes it playable again and again, and allows the magnetic information to be retrieved in playback on a tape machine.
Baking the tapes may have one beneficial and limited use for tape restoration under special conditions. If the Backcoating has turned into a strong glue which is ready to rip the Oxide off the Base of the tape, thus destroying the tape entirely, it would be useful to use the baking method, if doing so would melt or release the Backcoating""s grip on the Oxide long enough for the tape to be rewound and cleaned. If the Backcoating is removed, this is a way to prevent the Backcoating from stripping the Oxide from the base of the tape. In this limited instance, baking the tape in conjunction with the new process of cleaning of the present invention would work together to save the tape from destruction.
The present invention relates to a process for restoring magnetic recording tape damaged by xe2x80x9cSticky Shedxe2x80x9d syndrome. The present invention includes the following interrelated objects, aspects and features:
(1) The process cleans magnetic tapes of the Backcoating which is causing their eventual degradation and destruction. The invention works by first removing the Backcoating in a multi-step process. A liquid cleaner, such as Isopropyl Alcohol, is applied to the Backcoating to dissolve it from and clean it off the Mylar Base as much as possible.
(2) Before the liquid cleaner is applied, steps are taken to prevent the cleaner fluid from getting onto the Oxide side of the tape where the solvent cleaner would do damage if steps are not taken to prevent the solvent from getting onto the Oxide side of the tape. The chemical cleaning is done as quickly as possible to remove the Backcoating. Speed of cleaner application and removal of debris are also important to prevent the solvent from attacking the Base material of the tape.
(3) Immediately after the wet solvent cleaning and removal of the Backcoating is done, the second step is to do a dry-cleaning of the Base surface of the tape to remove the remaining solvent and the debris of any remaining Backcoating. After the removal of the Backcoating and the cleaning of the tape Base, the Oxide side of the tape is given a dry, non-chemical cleaning to remove, as best one can, the residue of contamination of the Backcoating which was deposited on the Oxide side of the tape as the result of physical contact with the Backcoating from the storage on the reel of tape and its layers, as well as any Backcoating residue that may have gotten on the Oxide from various mechanical elements in the tape path of a tape machine which itself was contaminated by the rub off of the Backcoating on the parts of the tape machine. Once fully and properly cleaned, the tape is restored to a useful and long life.
(4) A machine is employed to carry out various mechanical and chemical actions involved in the inventive process in a safe and logical manner. The machine handles the tapes in a safe manner and permits one to monitor the location of the tape where cleaning is taking place based upon the program material and/or measured length of the tape. A microscope or other magnifying device is also provided to allow monitoring of the effectiveness of cleaning operations.
As such, it is a first object of the present invention to provide a process for restoring magnetic recording tape damaged by xe2x80x9cSticky Shedxe2x80x9d syndrome.
It is a further object of the present invention to provide such a process in which a solvent such as Isopropyl Alcohol is applied to dissolve and remove the Backcoating from a length of magnetic recording tape.
It is a further object of the present invention to provide such a process in which steps are taken to preclude the solvent from damaging the Oxide side of the tape.
It is a still further object of the present invention to provide such a process in which dry-cleaning of the Base surface of the tape is carried out to remove residual solvent and debris from the Backcoated side of the tape.
It is a yet further object of the present invention to provide a such a process in which the Oxide side of the tape is dry cleaned to remove any solvent and Backcoat debris.
It is a still further object of the present invention to provide such a process in which dry-cleaning of the Oxide side of the tape is carried out to remove residual debris from the Oxide side of the tape.
It is a still further object of the present invention to provide such a process in which a machine is employed to wind and unwind the tape while the process is being carried out, while also being able to monitor the effectiveness of the process.
These and other objects, aspects and features of the present invention will be better understood from the following detailed description of the preferred embodiment when read in conjunction with the appended drawing figures.